Injection molding system with discretely-adjustable variable control

ABSTRACT

An injection molding machine uses a controller to effectively control its operation. The controller may determine and/or receive information regarding the machine&#39;s maximum load capacity, and may also determine a current operational load value of the machine. The controller also may determine a number of set points used to operate the machine. The controller may cause the machine to operate at these set points, thereby resulting in the machine operating at or below the maximum load value by adjusting any number of machine parameters associated with the injection molding machine.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/382,335 (filed on Sep. 1, 2016), the entirety of which isincorporated by reference herein.

FIELD OF THE DISCLOSURE

The present application generally relates to injection molding and, morespecifically, to approaches for adjustably operating an injectionmolding machine to reduce the energy required to form a molded article.

BACKGROUND

Injection molding is a technology commonly used for high-volumemanufacturing of parts constructed of thermoplastic materials. Duringrepetitive injection molding processes, a thermoplastic resin, typicallyin the form of small pellets or beads, is introduced into an injectionmolding machine which melts the pellets under heat and pressure. Themolten material is then forcefully injected into a mold cavity having aparticular desired cavity shape. The injected plastic is held underpressure in the mold cavity and subsequently is cooled and removed as asolidified part having a shape closely resembling the cavity shape ofthe mold. A single mold may have any number of individual cavities.

Injection molding machines operate within manufacturer-providedconstraints to ensure safety and operability of the machine. Thesemachines are typically constrained by maximum load values which act tolimit any number of operating parameters of the injection moldingmachine to ensure safe and effective operability and avoid damage tocomponents of the injection molding machine. In the event that themanufacturer's safety margin level, as contrasted to the machine'sactual maximum load value for a given set of operating and environmentalconditions, is exceeded, the machine may overheat, trip to a failsafesetting, and/or trigger an alarm condition. The maximum load value maybe represented graphically, and it may be dependent on any number ofvariables, such as, for example, equipment operating speeds, pressures,the type and viscosity of material(s) being molded, as well asenvironmental conditions. Because of the presence of maximum loadvalues, the machine may be permanently configured to operate at or belowparticular variables regardless of whether the machine is operatingabove the maximum allowable load prescribed by the manufacturer.

Generally speaking, injection molding machines allow an operator tomodify and/or manipulate the operating parameters thereof. As a merelyillustrative, non-limiting example, if an environmental factor such as aplant ambient temperature causes the injection molding machine to workharder (i.e., consume more energy) to generate parts, the machine'soperating load value over a given period of time will increase. Thisincrease in the operational load value may eventually cause the machineto approach or exceed the maximum load value which may result intemporary or permanent machine failure. Prior to exceeding or evenreaching this maximum load value, the machine may be pre-programmed togenerate an alarm which prompts a machine operator to adjust operatingvariables as required to lower the operating load on the machine, or maytrigger the machine to reduce or even cease molding operationsaltogether, i.e. trip to a safety mode.

Machines may be configured to provide a safety margin below a maximummachine load based on a “worst-case scenario,” that is, when any numberof parameters are present that would dramatically impact operability ofthe machine. The restrictions applied to the machines (e.g., safetyfactors) may restrict the machine from operating within a certainpercentage of the maximum machine load. As a result, in operatingconditions that resemble the worst-case scenario (such as environmentswith high ambient temperatures and/or pressures, materials havingabnormally high viscosities, thus impacting flow speeds and coolingtimes, and the like), the machine is limited to performing at a levelthat is less than its peak performance. Similarly, even in the presenceof operating conditions which are considered favorable or preferred, dueto the fact that the manufacturer's pre-programmed safety factors areset with worst-case scenarios in mind, and are often not easilyoverridden, it is often the case that conventional injection moldingsystems do not approach peak efficiency outputs, even in the most idealof operating conditions.

Frequently, injection molding machines are configured by themanufacturer to fix the range of adjustability of certainoperator-adjustable parameters in an injection molding operation, oreven prevent any operator adjustment of certain parameters, based onoperator adjustment of other parameters. For instance, if an operatorsets up an injection molding machine to implement molding operatingprogram that contemplates injecting a viscous molten thermoplasticmaterial at particularly aggressive velocity in a given portion of eachinjection molding cycle, the machine may be pre-programmed to onlypermit the injection molding machine's electric, hydraulic,servo-hydraulic, or servo-driven screw to accelerate at a conservativerate of acceleration, and/or to operate at a conservative pressure,based on the manufacturer's built-in safety margin below the machine'sactual load capacity.

SUMMARY

Embodiments within the scope of the present disclosure are directed tothe use of a controller or controllers capable of effectivelycontrolling operation of an injection molding machine, which may be apreviously-installed machine or an original equipment manufacturer (OEM)injection molding machine. The controller(s) may determine and/or obtaininformation regarding the machine's maximum load capacity based at leastin part on any number of critical design limitations, and may alsodetermine an instantaneous (or at least periodic) present load value onthe machine. The controller(s) may determine, calculate, or otherwiseidentify any number of critical design limitations and determine anumber of discrete set points in which the machine can be operated thatfall below the critical design limitations. The controller(s) of thepresent disclosure may allow the machine to be operated at or near themaximum load value by adjusting any number of machine parametersaccording to each of the discrete set points, and can dynamically adjustthe range within which operator-adjustable parameters in an injectionmolding operation may be manipulated to facilitate, or at least permit,operation of the injection molding machine in a manner that exploits themachine's actual load capacity during the course of its operation,thereby increasing efficiency and output. In response to operatoradjustment of various injection molding operating parameters, ratherthan constrain other operating parameters to tight ranges or preventingadjustment beyond conservative manufacturer-set safety margins, thecontroller(s) of the present disclosure permits conventionally-fixedparameters to float in a manner that allows the injection moldingmachine to operate at, or near, its maximum load capacity at the newoperating conditions (which may include both machine conditions andenvironmental conditions).

In many embodiments of the present disclosure, the controller(s) may beadapted to selectively operate the injection molding machine in a mannerthat allows the current load value to remain, on average (e.g., a timeloaded average), below the maximum load value over a specified period oftime. By adjusting any number of operating parameters, the machine iscapable of reacting to changing conditions, some of which may occurduring the middle of a cycle, in a near-instantaneous manner, thuseffectively maximizing machine efficiency and producing the maximumnumber of parts possible over a given period of time. Additionally,because the controller is adapted to monitor the machine in real-time,an operator need not actively monitor and/or adjust the machine'sparameters on the fly.

In these embodiments, the controller may first enter into a learningmode, during which an initial or reference load value or curve isobtained. In some of these examples, the initial load value is input ordownloaded to the controller by a manufacturer prior to the system beinginstalled in its operating environment. In other examples, the initialload value is calculated in the environment and is based on a first setof parameters and/or operating variables, and represents an estimatedmaximum load value the injection molding machine can maintain over agiven period of time while avoiding failure. The controller thencalculates a modified load value by operating the injection moldingmachine based on a second set of operating variables. This second set ofparameters may be values that are anywhere between approximately 0.1 to50%, preferably 0.1 to 25%, more preferably 0.1 to 15%, even morepreferably 0.1 to 10%, and most preferably 0.1 to 5%, including anyinteger or non-integer percentage within these ranges, away from theparameters used to calculate the initial load value. The load values maybe calculated using a root-mean-square approach or any other suitablemethod.

Using the initial and modified load values as well as the first andsecond set of operating parameters, a reference (or maximum) load curvefor that particular injection molding system may be generated. Forinstance, a computer program associated with the controller may beprovided that interpolates load values between the measured initial andmodified load values for any operating conditions intermediate the firstand second operating conditions, and extrapolates load values foroperating conditions outside of the first and second operatingconditions. Alternately, a reference or maximum load curve may beprovided by the machine manufacturer or by the provider of theequipment, may be a theoretical value based on a predetermined maximumoperating condition, and/or may be obtainable by other means.

The operating parameters may be any combination of adjustments to theinjection molding machine, and may include environmental conditions,some of which may be within the control of the molder, such as ambienttemperature in a temperature-adjustable manufacturing facility, but somemay be outside of human control, such as barometric pressure. In someapproaches, variations in operating parameters may include adjustmentsto a barrel temperature, a clamp closing speed, a clamp opening speed, acooling time, an inject forward time, an overall cycle time, a pressuresetpoint, a screw recovery speed, and a screw velocity. Other examplesare possible and may be dependent on the particular injection moldingmachine in use.

After determining or otherwise obtaining the reference load curve, thecontroller may then obtain a plurality of discrete set points along thereference load curve. These set points are constrained by criticaldesign elements or limitations which are depicted as extremes ornear-extremes on the reference load curve. These limitations representconditions in which the machine cannot exceed on any circumstances,otherwise machine failure would occur. The controller can select anynumber of discrete set points to be used to operate the machine. Thediscrete set points can be obtained by the machine by adjusting anynumber of machine parameters described herein. In some examples, betweentwo and ten set points may be used. Other examples are possible.

Upon the machine entering an operational mode, the controllerselectively operates the machine by designating any one of the discreteset points at which to operate. The controller can change set points atany time, and an operator may also explicitly select a set point. Byadjusting the various operating parameters, an operational load value ofthe machine may be maintained below the reference load curve. Duringoperation of the machine, the controller is adapted to actively (e.g.,periodically) monitor the load values to ensure the operational load onthe machine remains below values of the reference curve. The controlleris further adapted to adjust the operating variables by switching to adifferent discrete set point as needed to ensure the operating loadvalue remains below the reference load values.

In many of these examples, the controller may selectively control howclosely the operational load is kept to the reference load curve byadjusting the operating parameters described herein. For example,depending on the particular application, the operational load may beheld to within approximately 0.1-50% of the maximum load value, or anyinteger or non-integer value for percentage in that range, or any rangeformed by any of those integer values, such as 0.1-30% or from 0.1-25%,0.1-10%, or 0.1-5%.

The controller can be any type of controller, such as anelectro-mechanical controller, a circuit board, a programmable logiccontroller, an industrial computer, or any other type of controller asdescribed herein or as known in the art. The controller may be set,configured, and/or programmed with logic, commands, and/or executableprogram instructions according to the embodiments provided herein or asknown in the art.

In embodiments where multiple controllers are used (e.g., a nativecontroller and a retrofit controller which overrides operation of themachine), the retrofit controller is adapted to establish signalcommunication between the retrofit controller and the injection moldingmachine such that the retrofit controller at least partially controlsoperation of the machine. Thus, the retrofit controller may connect oneor more outputs from any number of sensors (e.g., pressure sensors,temperature sensors, position sensors, and the like) disposed on or nearthe machine to one or more inputs of the retrofit controller. Connectingthe retrofit controller may also include disconnecting one or more ofthe existing sensor outputs from the native controller and connectingthose existing sensor outputs to the retrofit controller, or adding moreoutputs to one or more of the existing sensors and connecting thoseadded outputs to the retrofit controller, or combinations of these.Connecting the retrofit controller can involve one or more existingsensors already in place on the molding machine, or moving one or moreexisting sensors to new locations on the molding machine, or installingone or more new sensors on the molding machine, or combinations ofthese. The signal communication can be any kind of signal (e.g.hydraulic, pneumatic, mechanical, analog electrical, digital electrical,optical, etc.) described herein or known in the art. In someembodiments, the retrofit controller can replace the native controllerand replace all of its functions. In other embodiments of retrofitting,the retrofit controller can be added as an addition to the nativecontroller and replace less than all of its functions. In alternativeembodiments, a native controller can be reconfigured to become aretrofit controller, as described herein.

Any or all of the embodiments described in this Summary section can beperformed in any way disclosed herein or known in the art, and can beused and/or combined in any workable combination, including anyalternative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The above needs are at least partially met through provision of theinjection molding machine with discretely-adjustable variable controldescribed in the following detailed description, particularly whenstudied in conjunction with the drawings, wherein:

FIG. 1 illustrates an exemplary machine loading profile in which aninjection molding machine's screw velocity is plotted as a function ofpressure in accordance with various embodiments of the presentdisclosure;

FIG. 2 illustrates an elevation view of an exemplary injection moldingmachine having multiple controllers coupled thereto in accordance withvarious embodiments of the present disclosure;

FIG. 3 illustrates portions of a control mechanism having a native and aretrofit controller capable of selecting discrete set points inaccordance with various embodiments of the present disclosure;

FIG. 4 illustrates a retrofit injection mold cycle as programmed to thecontrol mechanism to control the injection molding process in accordancewith various embodiments of the present disclosure;

FIG. 5 illustrates an exemplary screenshot of a controller providingperiodically updated operating values of a number of parameters inaccordance with various embodiments of the present disclosure;

FIG. 6A illustrates exemplary schematics of a control process of anelectric injection molding machine in accordance with variousembodiments of the present disclosure; and

FIG. 6B illustrates exemplary schematics of a control process of ahydraulic injection molding machine in accordance with variousembodiments of the present disclosure.

Skilled artisans will appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions and/or relative positioningof some of the elements in the figures may be exaggerated relative toother elements to help to improve understanding of various embodimentsof the present disclosure. Also, common but well-understood elementsthat are useful or necessary in a commercially feasible embodiment areoften not depicted in order to facilitate a less obstructed view ofthese various embodiments. It will further be appreciated that certainactions and/or steps may be described or depicted in a particular orderof occurrence while those skilled in the art will understand that suchspecificity with respect to sequence is not actually required. It willalso be understood that the terms and expressions used herein have theordinary technical meaning as is accorded to such terms and expressionsby persons skilled in the technical field as set forth above exceptwhere different specific meanings have otherwise been set forth herein.

DETAILED DESCRIPTION

Turning now to the drawings, an injection molding process is hereindescribed. Injection molding machines (also referred to herein simply as“machines”) have a generally nonlinear reference or maximum loadingcurve 10 as illustrated in FIG. 1. This curve 10 may be viewed as agraphical representation of an effect that any number of parameters or“critical design elements” (such as, for example, velocity as a functionof operating pressure), may have on the machine. Generally speaking,operators run these machines at operating load values (which mayfluctuate over time) that are at a point well below the reference loadcurve to avoid tripping the injection molding machine manufacturer'spre-programmed alarms and/or failure modes. As FIG. 1 illustrates,injection molding machines typically have absolute maximum operatingvalues that are dependent on the critical design element or elementswhich may not be exceeded so as to limit potential machine failure.

Machine manufacturers utilize safety buffers which act to restrictparameters from exceeding particular values that are lower than thatwhich would cause the machine to operate to its absolute maximumoperating load capacity. As illustrated by FIG. 1, points P-1 and V-1represent specified manufacturing maximum values that may not beexceeded. These values are programmed into a native controller that atleast partially controls operation of the machine. As a result of theserestrictive values, the typical available operating range 12 (asdepicted by the slashed shaded area in FIG. 1) is available for use bythe operator, meaning the operating parameters may fall somewhere inthis area.

However, the machine may still be operated using parameters that aregreater than the manufacturer's designated maximums without causingdamage to the injection molding machine. In the examples providedherein, operating parameters such as the maximum pressure areselectively increased (while remaining below the machine's specifiedabsolute maximum operating velocity value) in order to increase theavailable operating range 14 (depicted by area having circles in FIG.1). This range 14 generally depicts parameters used to create thinwalled components. Similarly, the maximum velocity may be selectivelyincreased (while remaining below the machine's specified absolutemaximum operating velocity value) in order to increase the availableoperating range 16 (as depicted by the area having crosses in FIG. 1).Any number of parameters may be adjusted in this way to increase theallowable operating range of the machine. Ultimately, the entire areaunder the maximum load curve (up to the machine's specified absolutemaximum or critical operating element parameter values) may be used.

As depicted in FIG. 1, any number of discrete operating set pointslocated along the maximum load curve can be selected using any number ofapproaches. These operating points may be evenly distributed along thecurve, or can be distributed in any desired manner based on theparticular machine's operating characteristics. For example, if it isdesired that a machine be designed to operate at high velocities withlittle need for high pressure operation, a number of discrete set pointswill be selected on the high velocity side of the curve.

To enable operating parameter values beyond the manufacturer'spreprogrammed maximums, a retrofit controller can be used to interceptand alter and/or generate new control signals that are sent to theinjection molding machine. The retrofit controller may include softwarethat communicates with the native controller to “trick” the nativecontroller into believing operating parameters are still within themanufacturer's maximum allowed values while in reality, differentcontrol signals are being sent to the machine. In some examples, theretrofit controller may suspend or intercept control signals originatingfrom the native controller and generate new signals to send to themachine. Other examples are possible, and further discussion of theretrofit controller is provided herein.

While any number of approaches may be used to form parts, the injectionmolding machine described herein is merely exemplary and is not intendedto limit the applicability of inventive concepts in any way. Theapproaches described herein may be suitable for electric presses,servo-hydraulic presses, and other known machines. As illustrated inFIG. 2, the retrofitted injection molding machine 100 includes aninjection unit 102 and a clamping system 104. The injection unit 102includes a hopper 106 adapted to accept material in the form of pellets108 or any other suitable form. In many of these examples, the pellets108 may be a polymer or polymer-based material. Other examples arepossible.

The hopper 106 feeds the pellets 108 into a heated barrel 110 of theinjection unit 102. Upon being fed into the heated barrel 110, thepellets 108 may be driven to the end of the heated barrel 110 by areciprocating screw 112. The heating of the heated barrel 110 and thecompression of the pellets 108 by the reciprocating screw 112 causes thepellets 108 to melt, thereby forming a molten plastic material 114. Themolten plastic material 114 is typically processed at a temperatureselected within a range of about 130° C. to about 410° C.

The reciprocating screw 112 advances forward and forces the moltenplastic material 114 toward a nozzle 116 to form a shot of plasticmaterial which will ultimately be injected into a mold cavity 122 of amold 118 via one or more gates 120 which direct the flow of the moltenplastic material 114 to the mold cavity 122. In other embodiments, thenozzle 116 may be separated from one or more gates 120 by a feed system(not illustrated). The mold cavity 122 is formed between the first andsecond mold sides 125, 127 of the mold 118 and the first and second moldsides 125, 127 are held together under pressure via a press or clampingunit 124.

The press or clamping unit 124 applies a predetermined clamping forceduring the molding process which is greater than the force exerted bythe injection pressure acting to separate the two mold halves 125, 127,thereby holding together the first and second mold sides 125, 127 whilethe molten plastic material 114 is injected into the mold cavity 122. Tosupport these clamping forces, the clamping system 104 may include amold frame and a mold base, in addition to any other number ofcomponents.

Once the shot of molten plastic material 114 is injected into the moldcavity 122, the reciprocating screw 112 halts forward movement. Themolten plastic material 114 takes the form of the mold cavity 122 andcools inside the mold 118 until the plastic material 114 solidifies.Upon solidifying, the press 124 releases the first and second mold sides115, 117, which are then separated from one another. The finished partmay then be ejected from the mold 118. The mold 118 may include anynumber of mold cavities 122 to increase overall production rates. Theshapes and/or designs of the cavities may be identical, similar, an/ordifferent from each other.

In examples where the injection molding machine is retrofitted, themachine 100 also includes a native controller 130 which iscommunicatively coupled with the machine 100 via connection 132. Theconnection 132 may be any type of wired and/or wireless communicationsprotocol adapted to transmit and/or receive electronic signals. In theseexamples, the native controller 130 is in signal communication with atleast one sensor, such as sensor 128 located in the nozzle 116 and/or asensor 129 located proximate an end of the mold cavity 122. Any numberof additional sensors may be placed at desired locations of the machine100.

The native controller 140 can be disposed in a number of positions withrespect to the injection molding machine 100. As examples, the nativecontroller 140 can be integral with the machine 100, contained in anenclosure that is mounted on the machine, contained in a separateenclosure that is positioned adjacent or proximate to the machine, orcan be positioned remote from the machine. In some embodiments, thenative controller can partially or fully control functions of themachine via wired and/or wired signal communications as known and/orcommonly used in the art.

The sensor 128 may be any type of sensor adapted to measure (eitherdirectly or indirectly) one or more characteristics of the moltenplastic material 114 located in the nozzle 116. The sensor 128 maymeasure any characteristics of the molten plastic material 114 that isknown in the art, such as, for example, pressure, temperature,viscosity, flow rate, and the like, or any one or more of any number ofadditional characteristics which are indicative of these. The sensor 128may or may not be in direct contact with the molten plastic material114. In some examples, the sensor 128 may be adapted to measure anynumber of characteristics of the injection molding machine 100 near thenozzle 116 and not just those characteristics pertaining to the moltenplastic material 114.

The sensor 128 generates a signal which is transmitted to an input ofthe native controller 140. If the sensor 128 is not located within thenozzle 116, the native controller 140 can be set, configured, and/orprogrammed with logic, commands, and/or executable program instructionsto provide appropriate correction factors to estimate or calculatevalues for the measured characteristic in the nozzle 116.

The sensor 129 may be any type of sensor adapted to measure (eitherdirectly or indirectly) one or more characteristics of the moltenplastic material 114 to detect its presence and/or condition in the moldcavity 122. In various embodiments, the sensor 129 may be located at ornear an end-of-fill position in the mold cavity 122. The sensor 129 maymeasure any number of characteristics of the molten plastic material 114and/or the mold cavity 122 that is known in the art, such as pressure,temperature, viscosity, flow rate, or one or more of any othercharacteristics that are indicative of any of these. The sensor 129 mayor may not be in direct contact with the molten plastic material 114.

The sensor 129 generates a signal which is transmitted to an input ofthe native controller 140. If the sensor 129 is not located at theend-of fill position in the mold cavity 122, the native controller 140can be set, configured, and/or programmed with logic, commands, and/orexecutable program instructions to provide appropriate correctionfactors to estimate or calculate values for the measured characteristicat the end-of-fill position. Any number of additional sensors may beused to sense and/or measure operating parameters.

The native controller 140 is also in signal communication with the screwcontrol 126. In these embodiments, the native controller 140 generates asignal which is transmitted from an output of the native controller 140to the screw control 126. The native controller 140 can control anynumber of characteristics of the machine, such as, for example,injection pressures (by controlling the screw control 126 to advance thescrew 112 at a rate which maintains a desired melt pressure of themolten plastic material 114 in the nozzle 116), barrel temperatures,clamp closing and/or opening speeds, cooling time, inject forward time,overall cycle time, pressure setpoints, screw recovery speed, and screwvelocity. Other examples are possible.

The signal or signals from the native controller 140 may generally beused to control operation of the molding process such that variations inmaterial viscosity, mold temperatures, melt temperatures, and othervariations influencing filling rate are taken into account by the nativecontroller 140. Adjustments between set points may be made by the nativecontroller 140 in real time or in near-real time (that is, with aminimal delay between sensors 128, 129 sensing values and changes beingmade to the process), or corrections can be made in subsequent cycles.Furthermore, several signals derived from any number of individualcycles may be used as a basis for making adjustments to the moldingprocess. The native controller 140 may be connected to the sensors 128,129, the screw control 126, and or any other components in the machine100 via any type of signal communication known in the art.

As illustrated schematically in FIGS. 2 and 3, the retrofit controller150 is generally similar to the native controller 140. The retrofitcontroller 150 is electrically coupled to the native controller 140 viaany number of methods such that the retrofit controller 150 and thenative controller 140 are in signal communication. The retrofitcontroller 150 is adapted to control operation of the injection moldingmachine 100 directly and/or by controlling the output of the nativecontroller 140.

The native controller 140 includes software 141 adapted to control itsoperation, any number of hardware elements 142 (such as a memory moduleand/or processors), any number of inputs 143, any number of outputs 144,and any number of connections 145. The software 141 may be loadeddirectly onto a memory module of the native controller 140 in the formof a non-transitory computer readable medium, or may alternatively belocated remotely from the native controller 140 and be in communicationwith the native controller 140 via any number of controlling approaches.The software 141 includes logic, commands, and/or executable programinstructions which may contain logic and/or commands for controlling theinjection molding machine 100 according to a mold cycle. The software141 may or may not include an operating system, an operatingenvironment, an application environment, and/or a user interface.

The hardware 142 uses the inputs 143 to receive signals, data, andinformation from the injection molding machine being controlled by thenative controller 140. The hardware 142 uses the outputs 144 to sendsignals, data, and/or other information to the injection moldingmachine. The connection 145 represents a pathway through which signals,data, and information can be transmitted between the native controller140 and its injection molding machine 100. In various embodiments thispathway may be a physical connection or a non-physical communicationlink that works analogous to a physical connection, direct or indirect,configured in any way described herein or known in the art. In variousembodiments, the native controller 140 can be configured in anyadditional or alternate way known in the art.

The retrofit controller 150 includes components that are similar tothose of the native controller 140, such as a software 151 adapted tocontrol its operation, any number of hardware elements 152 (such as amemory module and/or processors), any number of inputs 153, any numberof outputs 154, and any number of connections 155. The software 151 maybe loaded directly onto a memory module of the native controller 150, ormay alternatively be located remotely from the native controller 150 andbe in communication with the native controller 150 via any number ofcontrolling approaches. The software 151 includes logic, commands,and/or executable program instructions which may contain logic and/orcommands for controlling the injection molding machine 100 according todiscrete set points. The maximum allowable operating parameters are nolonger fixed to a single, permanent value and may be variable accordingto the number of discrete set points.

The connection 145 is illustrated as being in common with a connection155, wherein the common connection represents a pathway through whichsignals, data, and information can be transmitted: a) between theretrofit controller 150, the native controller 140 and the injectionmolding machine 100, b) between the retrofit controller 150 and theinjection molding machine 100, and c) between the retrofit controller150 and the native controller 140. In various embodiments these pathwaysmay be physical connections or non-physical communication links thatwork analogous to physical connections, direct or indirect, configuredin any way described herein or known in the art. In various embodiments,the native controller 140 and the retrofit controller 150 can beconfigured in any additional or alternate way known in the art.

FIG. 3 illustrates connecting a particular output 144 from the nativecontroller 140, which is used as a particular input 153 to the retrofitcontroller 150. In various embodiments disclosed herein, theretrofitting of the injection molding machine 100 includes establishingsignal communication between: a) an inject forward output 156 fromoutputs 144 of the native controller 140, and b) one of the inputs 153of the retrofit controller 150. The native controller 140 can be set,configured, and/or programmed with logic, commands, and/or executableprogram instructions such that the inject forward output 156 signalswhen the plastic injecting should (and/or should not) occur during amold cycle of the molding machine 100.

As an example, the native controller 140 can turn “on” the injectforward output 156 when the plastic injecting should occur, and can turn“off” the inject forward output 156 when the plastic injecting shouldnot occur. The retrofit controller 150 can use the state of the injectforward output 156 as a condition for injecting plastic in the moldcycle. This signal communication allows the native controller 140 tohand-off control of the plastic injection to the retrofit controller 150for the plastic injecting portion and/or any other portion of the moldcycle. In various embodiments, the function of the inject forward output156 can be accomplished by the native controller 140 sending to theretrofit controller 150 one or more additional or alternate signals,data, and/or information, which are equivalent to an inject forwardoutput 156, using any known approaches in the art.

FIG. 3 further illustrates moving a particular output from the nativecontroller 140 to the retrofit controller 150. In various embodimentsdisclosed herein, the retrofitting includes: a) disconnecting signalcommunication between an injection control output 147 of the nativecontroller 140 and a control input of an injection unit of the moldingmachine 100 (signal illustrated by a phantom line), and b) establishingsignal communication between an injection control output 157 of theretrofit controller 150 and the control input of the injection unit ofthe molding machine 100 (signal illustrated by a solid line). Theretrofit controller 150 can be set, configured, and/or programmed withlogic, commands, and/or executable program instructions such that theinjection control output 157 signals the injection unit regarding therate at which injecting should occur during plastic injecting of a moldcycle of the molding machine.

As an example, the retrofit controller 150 can generate the injectioncontrol output 157 as an analog control voltage, which scales from aparticular low value (representing a minimum injection rate) to aparticular high value (representing a maximum injection rate). Theinjection unit can use the state of the inject control output 157 as theinput for controlling the rate of injecting plastic in the mold cycle.The rate of injecting, in turn, directly affects operating values suchas the injection pressure of the molten plastic in the machine 100. As aresult, the injection control output 157 can effectively be used tocontrol injection pressures in the retrofitted injection molding machine100, according to any of the embodiments disclosed herein. This signalcommunication also allows the retrofit controller 150 to replace controlof the plastic injection by the native controller 140 in the mold cycle.In various embodiments, the function of the injection control output 157can be accomplished by the retrofit controller 150 generating one ormore additional or alternate signals, data, and/or information, whichare equivalent to an injection control output, and sending such to oneor more additional or alternate machine components, which partially orfully control operating parameters of the machine 100 in any way knownin the art. For example, in one alternative embodiment, the retrofitcontroller 150 may at least partially control injection pressures of themachine 100 by controlling a rate of melt flow through the nozzle 116.In various embodiments, the retrofitting can also include rerouting thedisconnected injection control output 147 to one of the inputs 153 ofthe retrofit controller 150. Other examples are possible.

The injection molding machine 100 may also include a disable switch 158,which can be provided with the retrofitting, as described herein. Thedisable switch 158 can allow a user of the retrofitted injection moldingmachine to select a mode of injection molding that disables the retrofitcontroller 150 such that the machine 100 and the native controller 140mold production versions (i.e. parts made using production conditions onthe molding machine 100, wherein the parts have acceptable part quality)of the plastic part according to the original mold cycle. In variousembodiments disclosed herein, the retrofitting process includesestablishing signal communication between: a) a user-controlled output159 from the disable switch 158, and b) one of the inputs 153 of theretrofit controller 150. The retrofit controller 150 can be set,configured, and/or programmed with logic, commands, and/or executableprogram instructions such that when the user-controlled output 159provides a particular signal, the retrofit controller 150 does notcontrol plastic injecting during a mold cycle of the molding machine100.

As an example, when the user-controlled output 159 is turned “on,” theinjecting function of the retrofit controller 150 is disabled and doesnot control the plastic injecting, and when the user-controlled output159 is turned “off,” the injecting function of the retrofit controller150 is not disabled and does control the plastic injecting. The retrofitcontroller 150 can also be set, configured, and/or programmed withlogic, commands, and/or executable program instructions such that whenthe injecting function of the retrofit controller 150 is disabled, theretrofit controller 150 can receive the control output 147 from thenative controller 140 (as described above) and pass that received signalto the control input of the injection unit of the molding machine 100.As a result, when the injecting function of the retrofit controller 150is disabled, the native controller 140 can effectively control theplastic injecting (with the passed through signal) and the retrofittedmolding machine 100 can still operate, although using an original moldcycle which is likely to be relatively less efficient than the presentmold cycle. In various embodiments, the function of the disable switch158 and the user-controlled output 159 can be accomplished by one ormore additional or alternate user input devices and/or signals, data,and/or information which are equivalent, in any workable way known inthe art.

FIG. 4 provides an illustration of a retrofit injection mold cycle 300as programmed on the native controller 140 and the retrofit controller150 of FIGS. 2 and 3, for controlling the injection molding machine 100.The retrofit mold cycle 300 includes an operating sequence of injectingmolten plastic 310, according to control 302 by the retrofit controller150, and subsequently performing other functions according to control301 by the native controller 140. The injecting of the molten plastic310 includes an initial injecting portion 315, a filling portion 316,which includes using a target pressure 316-t, and a decreasing pressureportion 317. The native controller 140 and retrofit controller 150 canuse various signal communications, as described herein and known in theart, to share control of the retrofitted injection molding machine 100during the retrofit mold cycle. The injecting of the molten plastic 310can be partially or fully performed in any way described herein for aretrofit mold cycle. The other functions of the cycle include coolingthe plastic 320, opening the mold 330, ejecting the part from the mold340, and closing the mold 350. Any number of additional functions may beperformed by either the retrofit controller 150 and/or the nativecontroller 140.

In order to run the retrofit injection mold cycle, machine load valuesmust be determined and/or calculated for the injection loading machine100, preferably in real time, continuously, semi-continuously,periodically, or at least one or a plurality of locations during thecourse of an injection molding cycle.

In some embodiments, maximum and/or reference load values for themachine 100 are provided by the manufacturer and/or are readilyobtainable and input onto the controller 140. In these examples, themaximum load values can be based on a critical design element whichdetermines an upper operating limit. Examples of critical designelements can include particular components (e.g., hydraulic hoses,hydraulic motor blocks, screw and/or check valves, and check rings)having designated pressure limitations. In order to operate the machineat higher levels, it must be verified that the components can withstandthe increase in operational load. Similarly, a maximum pressure alarmmay be incorporated into the system coupled to an equipment shutoffmechanism which will disable the equipment when clamp tonnage orpressure limitations are exceeded. If it is desired to operate themachine at increased operational levels, the equipment alarms must bemodified accordingly.

When preparing the environment and determining appropriate systems to beused, properties of the injection molding machine must be taken intoaccount while reviewing a specified part design and cavity guidelines.Some machines are designed for the production of particular parts (e.g.,thin wall parts), whereas other machines can be used to produce variousparts. The critical design element is typically based on a maximumvelocity (e.g., a motor limitation, bearing or other component failure)and/or a maximum pressure allotment. Other examples are possible.Generally speaking, machine velocity and pressure limitations on eachshot (that is, the volume of material used to fill the mold cavity) isdependent on the part design and equipment limitations. Selecting aninjection molding machine having a shot capacity equal to approximatelytwice the expected shot size of the part typically provides a suitablevariable processing window. Further, selecting an appropriate clampingtonnage can be an important design consideration. Generally speaking,tonnage between 3 and 6 tons/in² is sufficient for the production ofmost products. Any suitable values and/or parameters may be used indesigning the system.

In other examples, the maximum load may be calculated by causing theinjection molding machine 100 to enter a learning mode during which aninitial load value is calculated based on operating the machine 100according to a first defined set of parameters. Accordingly, this firstset of parameters would be interpreted as a “maximum loading” value. Amodified load value is then calculated by operating the machine 100according to a second defined set of parameters. In some examples, theloading may be increased by a specified percentage to reach an absolutemaximum loading of the machine. By modifying the parameters to thesecond defined set, a relative weighting of what each factor contributesto the overall loading of the machine can be determined. As an example,by increasing the cooling time by a specified percentage, the amount themachine loading changes can be calculated. The second set of parameterscan be experimentally determined to understand the maximum amount ofchange that is allowable before a noticeable degradation in part qualityis observed. As a result, in some embodiments, a suitable operatingrange for each parameter is determined and thereafter used to formsatisfactory parts.

This second defined set of parameters can differ from the first definedset of parameters, preferably by at least approximately 5-35% in orderto allow the reference load curve to be optimally interpolated andextrapolated. The retrofit controller 150 and/or the native controller140 then generates and stores a reference load curve that is based onthe first and second operating parameters via extrapolation and/or anyother suitable method. For example, the parameters may be determined viaan iterative, “closed-loop” process known in the art. In these examples,limits and operating instructions must be established and provided sothe controller can “learn” how far the parameters may be changed tomaintain safe operation of the injection molding machine. In furtherembodiments, dependent variables may be added where modifying any numberof variables may result in other variables automatically changing tostay within the established limits.

In some examples, it may be necessary to identify operating speed,torque settings, estimated load values, the particular machine geometry(e.g., screw pitch or other details), and the type of plastic beingused. Other variables may also need to be identified. The reference loadcurve may be calculated via any other suitable method known in the artsuch as by experientially monitoring system performance at a peak periodof time and storing and using these values as maximums. In otherapproaches, the maximum load value may be a theoretical value based onthe motor and/or drive specifications for a given injection moldingmachine.

Next, absolute limits or critical design elements are determined for thecurve as previously described. These limits will act as operationalconstraints in which the machine cannot exceed under safe operation. Anumber of discrete operating set points are selected between theselimits. In some examples, a first central set point can be recommendedand/or provided by the manufacturer. Accordingly, any number ofadditional set points can be determined which fall on either side of thecentral set point. In some examples, the set points are equallydistributed along the load curve, and in other examples, the set pointsare distributed unequally, randomly, or in any other desired manner toprovide for control of the machine in a desired manner. For example, ifa particular machine exhibits operating efficiencies at or near aparticular location along the load curve, the discrete operating setpoints may be set near this range to take advantage of the efficiency.Other examples are possible.

Upon determining and/or establishing any number of set points, thelearning mode is complete, and the injection molding machine 100 isplaced in an operational mode wherein it is operated in a manner that inwhich an average load value does not exceed the maximum load value overa given time but may approach the maximum load value to obtain peakefficiency. In other words, the machine 100 may temporarily operate atvalues which are above the maximum load value, but over a given time,the average load value over the course of that interval will be belowthe max load value. This average load value over the course of aninterval that is all or some fractional portion of the load value over asingle cycle is referred to herein as an “average operational load valueof the injection molding machine.” Alternately, the learning mode mayremain open and the reference or maximum load curve could continually orperiodically be regenerated based on new reference load data. If theoperational load value were to exceed the maximum load value, themachine 100 may overheat, risk damage to one or more of its components,and/or fail.

The machine 100 may be adapted to accept a user input designating howclose an operational load must be to the maximum load allowable by themachine. In some embodiments, a user may wish to operate the machine 100within approximately 50% and approximately 100% of the maximum load atall times, without exceeding the maximum load at any time.

In preferred embodiments, the machine may be configured to operate atany numerical value between approximately 60-99% of the machine'smaximum load. If the operational load falls outside of this range, theretrofit controller 150 is adapted to selectively control operation ofthe machine by switching to a different set point to cause theoperational load to be within this range, with a pre-programmedhierarchy of operational parameter adjustments to be made to bring themachine back within the desired range. In some examples, sensors 128,129 and/or any other devices may determine values associated with themachine's 100 operation and transmit these data to the native controller140 and/or the retrofit controller 150. The current operating values arethen compared to the reference load curve to determine whether themachine is operating within the desired range.

In some embodiments, any or all of the initial load value, the modifiedload value, and/or the current operational load value are calculatedusing a root-mean-square (or RMS) calculation in which the operatingcurrent and/or voltage values are periodically measured to determine amean value. Power consumption can be measured using any number ofapproaches known in the art such as, for example, by usingcurrent/voltage probes. To measure power consumption, RMS voltage andRMS current are calculated and multiplied together. The powerconsumption may also be calculated using the following formula:

POWER=SQRT(I ₀ ² +I ₁ ² +I ₂ ² + . . . I _(n) ²)*SQRT(V ₀ ² +V ₁ ² +V ₂² + . . . +V _(n) ²)

where I_(n) and V_(n) represent scans of the processor. If these valuesare calculated at a high enough rate, a machine's power loading may beprovided. This calculation is then reset or repeated with each givenshot or segment of control of interest (for example, the injectionphase, the hold phase, the recovery phase, etc.). In other examples, amachine capacity load calculation or any other calculation known in theart may be used to determine the machine's load.

An exemplary operating screen or display 500 of the native controller140 and/or the retrofit controller 150 is illustrated in FIG. 5. Thenative controller 140 and/or the retrofit controller 150 may sense,determine, calculate, and/or display information relating to operationof the machine 100 in a graphical manner to allow an operator toidentify how the machine 100 is currently operating. The nativecontroller 140 and/or the retrofit controller 150 may also storehistorical data for the operator to review at a later date and toperform any number of analytical calculations. The display 500 mayprovide energy consumption metrics for different phases of the injectionmolding cycle, and may sum this information to provide a total loadvalue.

In some embodiments, the retrofit controller 150 may incorporate anynumber of approaches to providing periodic, accurate tracking and/oradjusting of machine parameters in real or near-real time. For example,the retrofit controller 150 may incorporate feedback control componentsand/or systems which compare real-time sensed operating values withanticipated operating values and applying corrective action tocompensate for the difference between the sensed values.

In some examples, the retrofit controller 150 may be a closed loopcontroller which provides feedback and trim control during the moldcycle. The feedback trim control provides modification to bothsteady-state response and control system dynamics. By altering thefeedback signal of the control system (e.g., adding and/or subtracting aPID controlled trim signal), either the native controller 140 and/or theretrofit controller 150 may perform the desirable process. Any number offeedback controllers and/or systems known those having skill in the artmay be used.

As a non-limiting example and as illustrated schematically by FIGS. 6Aand 6B, the retrofit controller 150 may be adapted to include feedbackcontrol (e.g., a trim control process as illustrated by FIG. 6A) whichcan include a number of components coupled to the injection moldingmachine 600 via any number of electrical coupling approaches. Thefeedback control may be applied to any machine configuration, includingelectric, hydraulic, servo-hydraulic, servo-driven, and any otherconfigurations. In addition to the components of the injection moldingmachine 600 previously described herein with regard to the precedingfigures, the process may utilize any number of sensors 602 (e.g., acavity sensor and a nozzle sensor), a load calculation module 604, afirst pressure setpoint 606, a first summer 608, a first PID controller610, a second summer 612, a second pressure setpoint 614 (which may beequal in value to that of the first pressure setpoint 606), a thirdsummer 616, a second PID controller 618, and a valve or drive 620. Anynumber of additional components used in feedback control processes mayalso be used to provide control. Further, the native controller maysupply the retrofit controller with any number of sensed values notillustrated in FIGS. 6A and/or 6B.

As illustrated in FIG. 6A, the sensor and/or sensors 602 transmit asignal to the load calculation module 604 to determine the currentoperational load value. This value is transmitted to the first summer608 which compares the value to the first pressure setpoint 606 andgenerates an error signal to be transmitted to the first PID controller610. The first PID controller 610 then generates a load signal andtransmits the signal to the second summer 612, which compares the signalto the current operational load value. The second summer 612 generates avoltage signal indicative of an operating pressure based on the receivedsignals, and is compared to the second pressure setpoint 614 value atthe third summer 616. Depending on the machine, the system environment,and additional factors, the process may transmit signals at differentvoltage scales. For example, the signals may range between 4-20 mV,−10-10V, 0-10V, and any other suitable range. In some embodiments, thesignal ranges may also vary based on the type of signal being measured(e.g., a temperature, pressure, and/or position measurement). An errorsignal is again sent to the second PID controller, which generates avoltage signal representative of a valve position for the valve or drive620. Upon receiving this signal, the valve 620 adjusts and transmits apressure to the injection molding machine 600 for operation.

The process illustrated schematically in FIG. 6B depicts the use of acontrol loop in an exemplary standard (e.g., hydraulic) press anddiffers from the process in FIG. 6A in that a single control loop isused to determine and cause modifications to the system. In thesemachines, the feedback loop may be different from the control used in anelectric process. Some considerations when controlling a hydraulic pressinclude additional contributing factors on the load such as hydraulicpressure (including the pressure in hoses, valves, and othercomponents), oil temperatures (where, in some examples, the hybrid pressmay shut down due to overloading), and a PID tuning rate. Other examplesare possible.

In FIG. 6B, the sensor and/or sensors 602 transmit a signal to the loadcalculation module 604 to determine the current operational load value.This value is transmitted to the summer 608 which compares the value tothe pressure setpoint 606 and generates an error signal to betransmitted to the PID controller 610. The PID controller then generatesa voltage signal representative of a valve position for the valve ordrive 620. Upon receiving this signal, the valve 620 adjusts andtransmits a pressure to the injection molding machine 600 for operation.In some examples, the controller may adjust the dwell, cooling, and/oreject timing prior to adjusting valve pressure.

In some approaches, parameters of the injection molding machine 100 maybe adjusted in any number of ways to effectuate a change to the currentoperational load. For example, changes may be made to a barreltemperature, a clamp closing speed, a clamp opening speed, a coolingtime, an inject forward time, an overall cycle time, a pressuresetpoint, a screw recovery speed, and/or a screw velocity to adjust thecurrent operational load. Changing any and/or all of these parametersmay have an effect on the operational load, thus there may be countlessapproaches to modifying these parameters to accomplish an increase ordecrease in the operational load value.

For example, in some embodiments, by decreasing the barrel temperature,the machine's loading increases, as, for example, the lower barreltemperature may result in relatively higher viscosity of the moltenpolymeric material to be injected into the mold cavity. By decreasingthe clamp closing and opening speed, the operational load value willdecrease. By decreasing the cooling (or dwell) time, the operationalload value will increase. By decreasing the inject forward time (e.g.,fill and pack times), the pressure setpoint, screw recovery speed, andscrew velocity, the machine's loading values will decrease. Bydecreasing the overall cycle time, the machine's loading will increase.For any of the above examples, increasing the parameter may result in anopposite effect on the machine's loading. Other examples of parameterswhich may be adjusted are possible. The software 151 of the retrofitcontroller 150 is adapted to selectively adjust any number of theseparameters to increase or decrease the load value as desired to keep thecurrent operational load within the desired range.

While the examples described herein involve the use of a native and aretrofit controller capable of being adjusted according to a number ofdiscrete set points, an original equipment manufacturer (OEM) injectionmolding machine can alternately be programmed in such a manner. In otherwords, the “native” controller can be programmed to determine a numberof set points located outside of a typical operating parameter orparameters. As such, a machine can be provided with such an operatingfunctionality preinstalled. Appropriate sizing parameters of such OEMsystems must be determined based on the critical design elementspreviously described herein.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

All documents cited in the Detailed Description are, in relevant part,incorporated herein by reference; the citation of any document is not tobe construed as an admission that it is prior art with respect to thepresent disclosure. To the extent that any meaning or definition of aterm in this document conflicts with any meaning or definition of thesame term in a document incorporated by reference, the meaning ordefinition assigned to that term in this document shall govern.

While particular embodiments of the present disclosure have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the disclosure. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this disclosure.

What is claimed is:
 1. A method of operating an injection moldingmachine, the method comprising: providing an injection molding machinehaving a controller adapted to control operation thereof; entering alearning mode of the controller to obtain a reference load curve; uponobtaining the reference load curve, obtaining a plurality of set pointsalong the reference load curve; upon obtaining the reference load curveand the plurality of set points, entering an operational mode of thecontroller; and using the controller, operating the injection moldingmachine at one of the plurality of set points such that an averageoperational load value of the injection molding machine remains at orbelow the reference load curve.
 2. The method of claim 1, wherein thereference load curve is obtained by calculating an initial load value ofthe injection molding machine based on a first set of operatingparameters and calculating a modified load value of the injectionmolding machine by operating the injection molding machine based on asecond set of operating parameters.
 3. The method of claim 2, whereinthe initial load value is calculated by sensing at least one of a nozzlepressure, injection pressure, screw velocity, and voltage over apredetermined per-cycle period of time and calculating a load valueusing the sensed data.
 4. The method of claim 2, wherein the modifiedload value is calculated by sensing at least one of a nozzle pressure,injection pressure, screw velocity, and voltage over a predeterminedper-cycle period of time and calculating a load value using the senseddata.
 5. The method of claim 1, wherein the reference load curve isobtained by manually inputting values into a computer interface.
 6. Themethod of claim 1, wherein the plurality of set points are determined byobtaining at least one critical design operating pressure element,obtaining at least one critical design operating velocity element, anddefining the plurality of set points between the at least one criticaldesign operating pressure element and the at least one critical designoperating velocity element.
 7. The method of claim 6, wherein theplurality of set points comprise five values equally distributed alongthe reference load curve.
 8. The method of claim 1, wherein selectivelyoperating the injection molding machine comprises selectively adjustingat least one of barrel temperature, clamp closing speed, clamp openingspeed, cooling time, inject forward time, overall cycle time, pressuresetpoint, screw recovery speed, and screw velocity.
 9. The method ofclaim 1, wherein the controller comprises a closed loop controlleradapted to permit the injection molding machine unit to operate within50% of a given reference load value.
 10. The method of claim 1, whereinthe first set of operating parameters and the second set of operatingparameters comprise adjustments to at least one of barrel temperature,clamp closing speed, clamp opening speed, cooling time, inject forwardtime, overall cycle time, pressure setpoint, screw recovery speed, andscrew velocity.
 11. The method of claim 1, wherein the reference loadcurve provides an estimated maximum load value maintainable by theinjection molding machine while avoiding failure.
 12. The method ofclaim 1, wherein at least one of the initial load value, the modifiedload value, and the operational load value is calculated by at least onea root-mean-square load calculation and a maximum machine capacity loadcalculation.
 13. A discretely-adjustable injection molding systemcomprising: an injection molding machine comprising an injection unitand a mold forming a mold cavity, the injection unit adapted to receiveand inject a molten plastic material into the mold cavity to form amolded part; one or more sensors coupled to the injection moldingmachine; and a controller coupled to the injection molding machine andthe one or more sensors, the controller adapted to control operation ofthe injection molding machine; wherein the controller is adapted to:enter a learning mode to obtain a reference load curve using the one ormore sensors; obtain a plurality of set points along the reference loadcurve; enter an operational mode; and operate the injection moldingmachine at one of the plurality of set points such that an averageoperational load value of the injection molding machine remains at orbelow the reference load curve.
 14. The discretely-adjustable injectionmolding system of claim 13, wherein the controller obtains the referenceload curve by calculating an initial load value of the injection moldingmachine based on a first set of operating parameters and calculating amodified load value of the injection molding machine by operating theinjection molding machine based on a second set of operating parameters.15. The discretely-adjustable injection molding system of claim 13,wherein the controller comprises a computer interface that obtains thereference load curve via a plurality of manually inputted values. 16.The discretely-adjustable injection molding system of claim 13, whereinthe controller comprises a closed loop controller adapted to permit theinjection molding machine unit to operate within 50% of a givenreference load value